Often, a specific gap or preload is required between an unactuated piston assembly and the elements to be displaced when the piston is actuated. In some applications, for example in a disconnect system, the elements to be moved includes a clutch plate assembly comprising a series of non-friction plates and friction plates with varying tolerances, yielding an unpredictable assembled thickness. The varying tolerances make it desirable to adjust the gap or preload at assembly after the actual thickness of the series of clutch plates is determined. The gap or preload is controlled so that the disconnect system can engage in a controlled manner.
Some current disconnect systems include a shim that is placed in the piston assembly, for example between the piston face and the race of a thrust bearing to control the gap or preload between the piston assembly and the clutch plate assembly. The shim thickness is selected based on the particular clutch plate assembly thickness to maintain a specific gap or preload, or gap or preload range. The shim is an extra, loose component that adds no additional value to the disconnect system.
Accordingly, a need exists for an actuating piston with a selectable height to provide a specific gap or preload, or gap or preload range.